Ornithine transcarbamylase (OTC) deficiency is the most common urea cycle disorder. It is often thought of as a severe condition that mainly affects newborn boys. However, females represent a substantial and clinically important proportion of people living with OTC deficiency.
Because OTC deficiency is inherited in an X-linked manner, females can experience a wide and unpredictable range of symptoms. These may be mild or intermittent, or they may worsen over time and, in some cases, become severe or life-threatening.
Symptoms in females can be subtle and easy to miss
In many females, symptoms are not immediately recognised as being related to OTC deficiency. They may appear gradually, fluctuate over time, or become more noticeable only in certain situations.
Common symptoms can include:
- persistent fatigue or exhaustion
- “brain fog” or mental slowing
- headaches
- forgetfulness or memory difficulties
- difficulty concentrating or learning
- irritability, mood changes, or emotional instability
- poor appetite
- avoidance of protein-rich foods (such as meat, fish, dairy, or nuts), or feeling unwell after eating them
Because these symptoms are non-specific, they are often dismissed, normalised, or attributed to other causes, such as stress, migraine, mental health conditions, or hormonal changes.
As a result, many females remain undiagnosed for years. Some are only identified after long-standing unexplained health problems, while others are diagnosed following the identification of an affected male family member.
A common misconception with serious consequences
There is a persistent misconception that females are largely unaffected by OTC deficiency. In reality, many females experience clinically meaningful disease, particularly during periods of increased metabolic stress, such as:
- illness or infection
- fasting or reduced food intake
- pregnancy
- childbirth
- the postpartum period
Failure to recognise this variability can lead to preventable hyperammonaemic crises and cumulative neurological injury.
Why earlier recognition matters
Improved awareness and earlier identification of OTC deficiency in females can support proactive and personalised care, including:
- regular metabolic monitoring
- individualised dietary and pharmacological management
- strategies to reduce the risk of metabolic crises
- preconception counselling
- structured pregnancy and postpartum care planning
- family cascade testing
Recognising OTC deficiency in females as more than “just being a carrier” is essential to improving outcomes and reducing avoidable complications.
When to seek medical advice
If you or someone in your family experiences symptoms like those described above, especially if there is a family history of OTC deficiency or unexplained episodes of illness, it is important to seek medical advice.
A healthcare professional can assess symptoms, arrange appropriate testing, and refer to a metabolic specialist if needed. Early evaluation and ongoing monitoring can make a meaningful difference to long-term health and safety.